title: Excitable human dynamics driven by extrinsic events in massive communities.
abstract: Using empirical data from a social media site (Twitter) and on trading volumes of financial securities, we analyze the correlated human activity in massive social organizations. The activity, typically excited by real-world events and measured by the occurrence rate of international brand names and trading volumes, is characterized by intermittent fluctuations with bursts of high activity separated by quiescent periods. These fluctuations are broadly distributed with an inverse cubic tail and have long-range temporal correlations with a power spectrum. We describe the activity by a stochastic point process and derive the distribution of activity levels from the corresponding stochastic differential equation. The distribution and the corresponding power spectrum are fully consistent with the empirical observations.
authors.affiliation: Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark.
authors.forename: Joachim
authors.initials: J
authors.lastname: Mathiesen
authors.forename: Luiza
authors.initials: L
authors.lastname: Angheluta
authors.forename: Peter T H
authors.initials: PT
authors.lastname: Ahlgren
authors.forename: Mogens H
authors.initials: MH
authors.lastname: Jensen
mesh_terms: D000465:Algorithms; D003142:Communication; D006801:Humans; D020407:Internet / Q000706:statistics & numerical data* / Q000639:trends; D015233:Models, Statistical; D012919:Social Behavior; D013269:Stochastic Processes
keywords: extreme events; social networks; statistical mechanics